1. Field of the Invention
The present invention relates to a method and apparatus for duplicating digital data accompanied by degradation and, in particular, to such a method and apparatus in which duplicated digital data can be degraded like analog data only by exchanging a small amount of data between digital data duplicating apparatuses.
2. Description of the Related Art
Japanese Patent Laid-open publication 2004-30630 proposes a method (apparatus) for self-degrading digital data in which the quality of digital data is degraded with use (copy and/or move) of the digital data so that the digital data cannot be duplicated accurately across several generations.
In this method, digital data is received from a content source and the quality of the digital data is degraded based on a specified quality degradation policy or a degradation specification model. The thus degraded digital data is transmitted to its destination. The quality of the digital data would be further degraded successively with further use of the digital data at the destination and its subsequent stages.
However, in the method above, degraded digital data is duplicated by successively exchanging the digital data itself between digital data duplicating apparatuses, resulting in a problem of requiring a broadband network between the digital data duplicating apparatuses.